Spring dampened shedding device

ABSTRACT

A shedding device in a jacquard loom, for forming the lower shed, for instance, has a retracting spring which is rigidly anchored on one end in the loom or to the floor. To suppress the development of resonance in the spring, a core element is provided, which contacts the inside of the spring at points spaced apart from one another and forces the spring to take a course which deviates from the rectilinear. As a result, friction forces that contribute to damping the spring motion are created between the spring and the core element.

[0001] Particularly in jacquard looms, the heddles are necessarily moved in one direction while being pulled by a spring in the other direction. As a rule, the heddle is moved by the spring to form the lower shed. The spring is anchored on the other end in stationary fashion in the loom or to the floor and in every operating state keeps the harness cord and heddle under tension.

[0002] Like any spring-elastic system, the assembly comprising the spring, heddle and harness cord also exhibits resonance phenomena, including the propagation of undulations that pass through the linear system. The natural resonance of the system does not matter, as long as the rate of motion of the heddle is low compared to the resonant frequency. However, at the moment when the rate of motion of the heddle reaches the range of the resonant frequency, unwanted undulations occur in the spring. The undulations are induced in the spring by the motion of the heddle, and they travel toward the fixed end, where they are reflected and run back toward the heddle. Under unfavorable circumstances, it can even happen that the heddle loses tension, since the returning undulation in the connection between the spring and the heddle has a phase relationship counter to the motion initialized by the motion of the harness cord.

[0003] The resonance inside the spring also assures increased mechanical stress and premature breakage. Typical breakage points occur.

[0004] To damp the resonance in the spring, it is known from European Patent Disclosure EP 0 678 603 to provide the lower spring fastening point with a damping device. The lower spring fastening point comprises a plastic molded part, on which a threaded peg is embodied. The helical spring is screwed onto the threaded peg. The threaded peg, on its free end, has two legs that are movable spring-elastically counter to one another, which protrude into the interior of the spring and press against the spring. On the end remote from the threaded peg, the two legs are joined together again and merge with two further legs, which form an open fork.

[0005] It has been found that this type of spring damping is not unproblematic. If the contact pressure with which the legs act against the inside of the spring windings is too hard, no usable damping action ensues. Instead, the arriving undulations are reflected, largely unattenuated, at those points where the legs touch the inside of the spring. Conversely, if the contact pressure is too low, once again adequate damping does not ensue.

[0006] This unfavorable phenomenon is reinforced by the fact that the spring elasticity of the plastic exhibits fatigue and is also temperature-dependent.

[0007] Finally, it is not simple to thread the open ends of the legs into the spring.

[0008] With this as the point of departure, it is the object of the invention to create a shedding device in which the problems discussed above do not occur.

[0009] This object is attained according to the invention by the shedding device having the characteristics of claim 1.

[0010] As in the prior art, the heddle is kept taut between the harness cord and the helical spring. The end of the helical spring remote from the heddle is anchored in stationary fashion. To achieve the desired damping, there is a damping element, which at at least a plurality of spaced-apart points is in contact with the helical spring and imposes a nonrectilinear course on the originally straight helical spring. In this way, the helical spring is in contact with the damping element at points spaced apart from one another. The contact force of the helical spring on the damping element is determined by the intrinsic elasticity of the spring and by the extent of the deflection. Conversely, the elasticity of the damping element plays practically no role.

[0011] Because of the essentially point-type contact between the helical spring and the damping element, some of the vibration energy at every point of contact can be converted into friction. The reflections of the mechanical undulation that occur at the contacting points are quantitatively too slight to be capable of generating a significant returning undulation that could cause springs to break. Between the contacting points, conversely, the spring extends somewhat freely.

[0012] Since the extent to which the spring is pressed against the damping element depends only on the geometric extent of the nonrectilinear course that the helical spring assumes because of the damping element, very precisely replicable contact pressures are achieved. The modulus of elasticity of the steel helical spring is far less temperature-dependent than the modulus of elasticity of plastic, and moreover, the modulus of elasticity also varies less over time.

[0013] Finally, practically no permanent deformation in the steel spring in such a way that it gradually adapts to the nonrectilinear course of the damping element occurs. The damping element, conversely, compared to the resilience of the helical spring, need not have any elasticity at all. Relative to the force exerted by the helical spring, the damping element can be rigid, in such a way that it is not pressed into a different shape by the helical spring. In this way, it is possible to generate very precisely replicable contact pressures and thus very precisely replicable friction forces between the spring and the damping element.

[0014] In particular, it is possible to cause the damping element to interact with the helical spring over a comparatively very long distance.

[0015] It is moreover possible for the extent of deformation, that is, the wavelength and/or the amplitude that the damping element imposes on the helical spring, to vary over the length of the damping element. In this way, increasing damping or bunching of the vibration can be attained, for instance. In the direction of the heddle, the damping element is initially deformed relatively little out of the rectilinear course, and the deformation increases toward the anchoring end of the helical spring. Very good damping with only very slight dispersion is attained at the damping element.

[0016] The damping element is preferably a core element, which is disposed in the helical spring and is linear. This saves additional space for the damping element, because it is disposed at the point that is necessarily present anyway.

[0017] To achieve the desired deformation, the core element can have a nonrectilinear course that deviates from the rectilinear course. Another option is to use an intrinsically rectilinear core element, which has discretely distributed, bumplike protrusions or humps spaced apart from one another, with which the desired nonrectilinear course is imposed on the helical spring. The diameter in the region of the protrusion or hump is less than the inside width of the helical spring.

[0018] The core element with a nonlinear course is essentially a cylindrical configuration with an undulating course. The undulations expediently define a straight regression line, so that on average, a straight course of the spring comes about.

[0019] The undulating course can occur because the core element forms a helix, or because the core element forms undulations that are located in the same plane.

[0020] In each case, a projection of the core element on a plane generates a band with an undulating course, whose width is equivalent to the diameter of the core element and whose undulating nature essentially matches the undulating or helical course of the core element. The dimensions of the undulating course are expediently defined at this band created by projection in the plane. In the projection, the undulating course can be seen to have an undulation depth, measured on one edge of the band, between a crest and a trough of between 0.1 and 3 mm. The magnitude of this undulation rise depends on the ratio of diameters between the core element and the inside width of the helical spring and on how strongly the helical spring is deflected or is to be pressed against the core element. The spacings between the crest and trough can range between 2 and 20 mm.

[0021] In the case where protrusions or humps are used, they can be disposed along a helical line, or in the simplest case along a zigzag; that is, each two adjacent protrusions are located on opposite sides relative to the core element. The spacing between protrusions is expediently in the range between 5 mm and 30 mm, and preferably between 5 mm and 20 mm.

[0022] The protrusions or humps are expediently integral with the core element and can be formed on either by injection molding or in some other way, if the core element is produced in that shape by the creative shaping process. Another option is to create the humps by local deformation, such as by crimping to form ears. This last option is attractive if the core element comprises a permanently deformable material, such as metal.

[0023] The length of the core element is expediently such that at least one complete undulation with the above dimensions can be generated.

[0024] The core element can rest loosely in the helical spring or can be joined solidly to the lower anchoring means.

[0025] Thermoplastics such as polyamide, polyethylene and polyurethane, or such other materials as metal, ceramic, pressure-setting plastics or vulcanizable materials, can be considered as material for the core element.

[0026] The shedding device of the invention is preferably employed in jacquard looms. Because of its very good damping action and the little space required, however, the arrangement according to the invention is not limited to jacquard looms, but can also be employed in normal looms for producing unpatterned woven fabrics, or heddle machines. Accordingly, the shedding device is also for instance a heddle machine, a jacquard loom, or a comparable drive device for setting the heddles in motion.

[0027] To connect the heddle to the helical spring, the heddle can be provided on the applicable end of the heddle shaft with a plastic molded part, which by way of example has a thread that can be screwed into the helical spring.

[0028] Connecting the helical spring to the lower or upper anchoring element can be done as in the prior art.

[0029] Moreover, combinations of characteristics from the dependent claims that are not described here as a concrete exemplary embodiment are also claimed.

[0030] Refinements are also the subject of dependent claims. In the drawing, one exemplary embodiment of the subject of the invention is shown. Shown are:

[0031]FIG. 1, a schematic illustration of a shedding device of the invention;

[0032]FIG. 2, an enlarged view of the core element;

[0033]FIG. 3, the upper connection between the heddle shaft and the retracting spring;

[0034]FIG. 4, an enlarged view of another embodiment of the core element, with lateral protrusions or humps;

[0035]FIG. 5, the core element of FIG. 4, in a cross section taken at the level of a protrusion;

[0036]FIG. 6, an enlarged view of a core element of the invention, in which the protrusions are created by local deformation; and

[0037]FIG. 7, the core element of FIG. 6, in a cross section taken at the level of a protrusion.

[0038]FIG. 1, highly schematically, shows the functional parts of the shedding device that are essential to comprehension of the invention, in a jacquard loom. The shedding device includes a drive device 1, of which a roller train 2 is shown. From the roller train 2, a collet cord secured to a collet floor 3 extends and changes into a harness cord 4 that passes between a glass grate or a guide floor 5. The harness cord 4 travels on to a harness board 6, where it emerges at the bottom through a bore 7. On the lower end, that is, the end of the harness cord 4 that is remote from the roller train 2, a heddle 8 is secured. The heddle 8 has an eyelet or eye 9 for a warp thread 11. From the eye 9, an upper and lower heddle shaft 12, 13 extend, located on the same straight line. The lower end of the lower heddle shaft is connected to a retracting spring 14, which is anchored at 15 to the machine frame or to the floor.

[0039] The motion of the roller train 2 is transmitted to the heddle 8 via the harness cord 4. As a result, the harness cord 4 is pulled upward, and the eye 9 is pulled upward out of its neutral position to form the upper shed. This tenses the retracting spring 14 more strongly than in the neutral position of the heddle 8, which is equivalent to the closed shed. When the harness cord 4 is let down, the retracting spring 14 pulls the heddle 8 downward to the same extent as the harness cord 4 moves downward. As a result, the applicable warp thread 11 forms the lower shed.

[0040] As readily seen, the upward motion of the heddle 8 is a compulsory motion, which is imposed rigidly by way of the harness cord 4, which cannot stretch in the longitudinal direction. The opposite direction, conversely, is a motion brought about by the retracting spring 14 and in this sense is only conditionally compulsory or rigid.

[0041] The configuration comprising the harness cord 4, heddle 8, warp thread 11 and retracting spring 14 is a spring mass system that has one or more resonant frequencies. At high machine speeds, the frequency at which the heddle 8 is moved out of the neutral position with the shed closed into the position for the upper shed or into the position for the lower shed is approximately 10 Hz. These frequencies, which are imposed by the drive system 1, are on the order of magnitude of the resonant frequencies of the entire system, or the resonant frequency of partial systems. Moreover, harmonics also occur, and at these frequencies, undulations develop in the linear configuration between the harness board 6 and the anchoring point 15 in the retracting spring 14, and if appropriate countermeasures are not taken, they are reflected at the anchoring point 15 and become standing waves in the retracting spring 14. As a result, the retracting spring 14 is extremely severely stressed at certain points and tends toward breakage. To damp the resonances, the lower anchoring point of the retracting spring 14 is embodied as shown in FIG. 2.

[0042] For connecting the retracting spring 14, which is shown in fragments in FIG. 2, there is an anchoring element 16, embodied essentially in rodlike form. The anchoring element 16 has an eyelet 17 on its lower end that can be suspended from a suitable rail mounted in fixed fashion to the machine frame. An essentially cylindrical shaft 18 extends from the eyelet 17 and is provided with a collar 19 on its upper end. A male-threaded peg 21 extends above-the collar 19, concentrically to the shaft 18. The male-threaded peg has a length equivalent to approximately ten spring windings. The retracting spring 14 is screwed onto this threaded peg 21. The retracting spring 14 is a cylindrical spring, wound of cylindrical steel wire, in which the windings in the relaxed state as a rule rest on one another.

[0043] On its free end, the threaded peg 21 changes into a core element 22, which as shown has a nonrectilinear course. The core element 22 forms troughs 23 and crests 24. It is deformed in such a way that the surface defined by the troughs and crests defines a plane. This means that in a side view rotated 90°, compared to FIG. 2, the core element 22 has a straight course.

[0044] As can readily be seen, the trough 23 on the opposite side of the core element 22 leads to a crest, like the crest 24, which in the correspondingly opposite direction deforms the spring 14.

[0045] The core element 22 has a circular cross section at all points, and the diameter of the cross section is less, by about 5 to 30%, than the inside diameter of the helical spring 14. The diameter of the core element 22 can be constant over its length or can decrease toward the tip. The core element 22 is injection-molded in one piece from plastic along with the threaded peg 21, shaft 18 and eyelet 17. Suitable plastics are polyamide, polyethylene, polyurethane, and polyester.

[0046] The undulating course that the core element 22 describes is so pronounced that the troughs and crests 23, 24 of the helical spring 14 impose a corresponding course. The helical spring 14 no longer extends rectilinearly in the region of the core element but instead has a zigzag motion that corresponds to the core element 22, as represented by the dashed lines 25 and 26. The lateral deflection of the spring 14 is lessened in accordance with the difference in diameter between the outside diameter of the core element 22 and the inside width of the helical spring 14.

[0047] The form of illustration of the core element 22 in FIG. 2 is equivalent to a projection of the core element 22 onto a plane, specifically the projection in which the undulating band generated by the projection has the greatest amplitude. If each of the boundary lines thus obtained is considered to be the course of a vibration, and if the usual terminology for vibration is used for description, then the amplitude of the vibration from tip to tip is about 0.1 to 3 mm, and preferably 0.1 to 1 mm, while the wavelength of the vibration is between about 4 and 40 mm; both values can vary along the length of the core element 22.

[0048] The amplitude of the undulating line, that is, the extent of lateral deflection, can increase from the free end of the core element 22 to the threaded peg 21. As a result, it is attained that the spring 14 with its windings rests with low lateral force on the first crest, because it is not deformed as much as at a crest that is located closer to the threaded peg 21.

[0049] In FIG. 3, for the sake of completeness, finally the connection between the lower heddle shaft 13 and the retracting spring 14 is also shown. As can be seen there, a plastic molded part 27 is formed onto the free end of the heddle shaft 13 and corresponds in terms of its structure to the opposite end of the anchoring element 16. The plastic molded part forms a collar 28 and also a threaded peg 29 that extends coaxially to the heddle shaft 13. The threaded peg 29 has a male thread, which may be cylindrical or tapered, and onto which the retracting spring 14 is screwed, as described above, until the end strikes the collar 28, as shown.

[0050] The mode of operation of the core element 22 as a damping member in the spring 14 is approximately as follows:

[0051] When an impact is introduced from the upper end of the retracting spring 14 through the heddle 8, the impact travels as a wave in the direction of the anchoring element 16. The impact travels as a longitudinal wave over the taut retracting spring 14. In normal operation, care is taken to assure that the spring windings of the retracting spring 14 will not rest on one another in any operating situation. As a result of the impact wave, however, such contact can certainly occur.

[0052] In every case, the impact wave travels through the spaced apart windings of the spring, which now correspondingly reach the core element 22. Between the applicable moving spring windings and the respective crest 23, 24 of the core element, friction occurs. The friction converts the energy of motion of the spring windings into heat and thus draws energy from the system. Excessive increases in amplitude caused by resonance are effectively suppressed. In particular, the damping assures that an impact wave travelling in the direction of the threaded peg 21 will reach the end of the helical spring 14 that is fixed to the threaded peg 21 only in attenuated form and will cause a corresponding echo of reduced amplitude, which in turn is further attenuated in its return travel along the core element.

[0053] In this-way, the core element 22 effectively assures a suppression of standing waves on the retracting spring 14. The damping action by the core element 22, whose total length is between 5% and 40%, preferably 10% and 30% of the retracting spring 14 that is taut in operation, also assures that longer-frequency waves are effectively damped, in order to suppress the development of standing waves whose wavelength is on the order of magnitude of the taut spring.

[0054] For reasons of assembly the core element 22 should be joined integrally to the threaded peg 21. However, there is no necessity to do so. On the contrary, for producing its damping action, the core element can be provided at an arbitrary point. In particular, it would also be conceivable to connect the core element 22 integrally with the anchoring member 27, by way of which the lower heddle 13 is coupled to the retracting spring 14.

[0055] In FIG. 4, another exemplary embodiment for a core element 22 is shown, which serves to impose a nonrectilinear course on the helical spring 14, and at the same time, only point contact comes about between the core element 22 and the helical spring 14, in order to generate the above-described damping action.

[0056] The core element 22 comprises a straight shaft 31, whose diameter is markedly less than the inside width of the cylindrical interior inside the helical spring 14. Bumplike extensions or humps 32 are located along a helical line on the outside of the shaft 31. In this case, the bumps or extensions 32 are offset from one another by 90° each; that is, in projection, as shown in the cross section of FIG. 5, the result is a four-pointed star. Nevertheless, the greatest diameter in the region of each hump 32 is less than the diameter of the interior of the helical spring 14. However, since the projection of two diametrically opposed extensions 32 onto a plane that intersects the axis of the shaft 31 at a right angle is greater than the diameter, the helical spring 14 is forced out of its intrinsically exactly rectilinear shape into a shape in the form of a helical line.

[0057] The height of the hump 32, measured in the radial direction, relative to the axis of the shaft 31 and the spacing of the extensions 32, measured in the longitudinal direction of the shaft 31, define the force with which the helical spring 14 rests on the crests of the extensions 32.

[0058] In the embodiment of FIGS. 4 and 5, the core element 22 comprises a one-piece plastic molded part. The bumplike extensions 32 are formed on integrally. Their axial length is less than their axial spacing from one another. Instead of integrally forming the bumplike protrusions 32 onto a plastic molded part, the possibility also exists, as shown in FIG. 6, of using a core element 22 whose shaft 31 comprises an originally cylindrical metal wire. The protrusions or humps 32 are created by laterally crimping the starting material, so that as the cross section of FIG. 4 shows, the material is positively displaced radially outward. This creates “ears”, which protrude radially past the contour of the originally circular cross section. The effect is the same as is described above for the exemplary embodiment of FIG. 2. 

1. A shedding device (1) for a loom, in particular for a jacquard loom, having a drive device for generating a longitudinal motion; having at least one heddle (8), which includes an eyelet (9) and from which heddle shafts (12, 13) extend toward diametrically opposite sides, of which one heddle shaft (12) is coupled with the drive device (2); having a connecting device (27) on the other heddle shaft (13); having a helical spring (14), associated with the at least one heddle (8), of which spring one end is mounted on the connecting device (27) and serves to retract the heddle (8); having an anchoring device (16) for fixedly anchoring the other end of the helical spring (14); and having a damping element (22), which is in contact at least at a plurality of spaced-apart points with the helical spring (14) and forces a nonrectilinear course on the helical spring.
 2. The shedding device of claim 1, characterized in that the damping element (22) is a core element (22), which is disposed in the helical spring (14) and which is linear.
 3. The shedding device of claim 2, characterized in that the core element (22) has a nonrectilinear course.
 4. The shedding device of claim 2, characterized in that the core element (22) has discrete protrusions (32) spaced apart from one another along the length of the core element, and the diameter of the core element (22), measured at the height of a given protrusion (32), is less than the inside width of the helical spring (14).
 5. The shedding device of claim 2, characterized in that the core element (22) is a cylindrical or laterally flattened configuration, which has an undulating course.
 6. The shedding device of claim 2, characterized in that the core element (22) is shaped in undulating fashion in such a way that the undulations are located in the same plane.
 7. The shedding device of claim 2, characterized in that the core element (22) has a helical course.
 8. The shedding device of claim 2, characterized in that the core element (22) has a cross section that is essentially constant over the length.
 9. The shedding device of claim 2, characterized in that the projection of the core element (22) onto a plane produces an undulating band with two edges parallel to one another, and the undulating line that one of the edges describes has an amplitude, measured between a trough (23) and a crest (24), that is between 0.1 and 3 mm.
 10. The shedding device of claim 2, characterized in that the spacing between a crest (24) and a trough (23) is between 2 and 20 mm.
 11. The shedding device of claim 2, characterized in that the core element (22) is designed such that its projection produces at least one complete undulation.
 12. The shedding device of claim 4, characterized in that the protrusions (32) are disposed along a helical line.
 13. The shedding device of claim 4, characterized in that the protrusions (32) protrude alternately to different sides of the core element (22).
 14. The shedding device of claim 4, characterized in that the protrusions (32) are integral with the core element ( ).
 15. The shedding device of claim 4, characterized in that the protrusions (32) are created by local crimping of the core element (22).
 16. The shedding device of claim 4, characterized in that the protrusions (32) have a spacing from one another of between 5 mm and 30 mm, and preferably between 5 mm and 20 mm.
 17. The shedding device of claim 2, characterized in that the material for the core element is thermoplastic, such as polyamide, polyethylene and polyurethane, or some other material, such as metal, ceramic, pressure-setting plastic, or a vulcanizable material.
 18. The shedding device of claim 1, characterized in that the damping element (22) is solidly joined to the anchoring device (16) or to the connecting device (27).
 19. The shedding device of claim 1, characterized in that the drive device (1) is a shedding device of a jacquard loom.
 20. The shedding device of claim 1, characterized in that the connecting device (27) is formed by a plastic molded part, which is joined materially and/or by positive engagement to the applicable end of the heddle shaft (13).
 21. The shedding device of claim 18, characterized in that the connecting device (27) has a thread (29).
 22. The shedding device of claim 1, characterized in that the anchoring device (16) has a thread (21).
 23. The shedding device of claim 18 or 19, characterized in that the thread (21) is a male thread.
 24. The shedding device of claim 15, characterized in that the thread (21) is a tapered thread.
 25. The shedding device of claim 16, characterized in that the core diameter of the thread (21), beginning at the diameter value which is less than the inside width of the helical spring (14), increases to a diameter which is equal to or greater than the inside width of the helical spring (14).
 26. The shedding device of claim 1, characterized in that the helical spring (14) is a helical tension spring, in which the individual spring windings rest on one another in the relaxed state.
 27. The shedding device of claim 1, characterized in that the helical spring (14) comprises steel. 